linux-kernel - Re: [PATCH v3 2/3] bus: mhi: host: Add a new API for getting channel doorbell address

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Message-ID: <20240415120237.GG7537@thinkpad>
Date: Mon, 15 Apr 2024 17:32:37 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Qiang Yu <quic_qianyu@...cinc.com>
Cc: quic_jhugo@...cinc.com, mhi@...ts.linux.dev,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	quic_cang@...cinc.com, quic_mrana@...cinc.com
Subject: Re: [PATCH v3 2/3] bus: mhi: host: Add a new API for getting channel
 doorbell address

On Mon, Apr 15, 2024 at 04:49:04PM +0800, Qiang Yu wrote:
> Some controllers may want to know the address of a certain doorbell. Hence
> add a new API where we read CHDBOFF register to get the base address of
> doorbell, so that the controller can calculate the address of the doorbell
> it wants by adding additional offset.
> 
> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
> ---
>  drivers/bus/mhi/host/main.c | 17 +++++++++++++++++
>  include/linux/mhi.h         |  7 +++++++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
> index 15d657a..947b5ec 100644
> --- a/drivers/bus/mhi/host/main.c
> +++ b/drivers/bus/mhi/host/main.c
> @@ -1691,3 +1691,20 @@ void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev)
>  	}
>  }
>  EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);
> +
> +int mhi_get_channel_doorbell(struct mhi_controller *mhi_cntrl, u32 *chdb_offset)

s/mhi_get_channel_doorbell/mhi_get_channel_doorbell_offset

> +{
> +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> +	void __iomem *base = mhi_cntrl->regs;
> +	int ret;
> +
> +	/* Read channel db offset */

No need of this comment.

> +	ret = mhi_read_reg(mhi_cntrl, base, CHDBOFF, chdb_offset);
> +	if (ret) {
> +		dev_err(dev, "Unable to read CHDBOFF register\n");
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}

Why can't you use this API in mhi_init_mmio()?

> +EXPORT_SYMBOL_GPL(mhi_get_channel_doorbell);
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index 8280545..1135142 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -816,4 +816,11 @@ int mhi_queue_skb(struct mhi_device *mhi_dev, enum dma_data_direction dir,
>   */
>  bool mhi_queue_is_full(struct mhi_device *mhi_dev, enum dma_data_direction dir);
>  
> +/**
> + * mhi_get_channel_doorbell - read channel doorbell offset register to get

'Get the channel doorbell offset'

> + *                            channel doorbell address
> + * @mhi_cntrl: MHI controller
> + * @chdb_offset: channel doorbell address

s/channel doorbell address/Channel doorbell offset

- Mani

-- 
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